1. Field of the Invention
The present invention relates to a cable reel, also known as a rotary connector, used in steering systems. The steering system includes a steering wheel installed in vehicles such as automobiles. The invention also relates to a method of assembling such a cable reel, in which the number of assembly steps is reduced.
2. Description of Background Information
In automobiles, a cable reel--or rotary connector--is used for electrically connecting electrical equipment installed on a steering wheel to chassis-side circuits. The mounting of the assembly shall be described with reference to FIGS. 1 and 2. The cable reel 1 is wound with a flat cable, and includes a rotor 5 which is rotatable within a cylindrical casing 2. As shown in FIGS. 1 and 2, the cylindrical casing 2 is fixed onto a combination switch body 3, which in turn is fitted to a steering column 4. On the other hand, there is provided a rotor 5 which rotates with a steering wheel. When the cylindrical casing 2 and the rotor 5 are assembled, they form a cylindrical space in which the cable reel 1 is installed such that the flat cable 6 is wound around the cable reel 1 in the manner of a coiled hairspring. End portions of the flat cable 6 are joined, respectively, to a first connector and a second connector. The first connector is fixed to the cylindrical casing 2, whereas the second connector is fixed to the rotor 5. An electrical cable is joined to each of the connectors 7 and 8 by one of its end portions, the other end portion of the cable being led out from the above assembly. As the rotor 5 rotates clockwise or counterclockwise relative to the steering wheel, the flat cable 6 can be made correspondingly tight or loose in the cylindrical space.
The method of assembling cable reel 1 is shown in FIG. 3. In this figure, a flat cable 6 is unrolled from a coiled reel 10 of flat cable 6, with the unrolled part of the flat cable temporarily set aside in a looped state. After a predetermined length of flat cable 6 is unrolled, the unrolled flat cable 6 is cut off from the rest of the reel 10. Both ends of the temporarily looped length of flat cable 6 are then respectively connected to a first connector 7 and a second connector 8, both of which are already connected to a respective electrical cable w. To connect the flat cable 6 to the first connector 7 and second connector 8, the elongate conductive portion (copper strip) of flat cable 6 is first welded to the core portion of electrical cable w. Then, the welded parts are each held by a connector housing.
In order to connect the flat cable 6 to the connectors 7 and 8, the temporarily looped flat cable 6 has to be straightened out. Then, one end portion of flat cable 6 is joined, e.g. to connector 7, whereas the other end portion is joined to connector 8. After the connector 7 is fitted to a top plate of rotor 5, the flat cable 6 is wound around the axial direction of rotor 5. On the other hand, connector 8, which is joined to the other end portion of flat cable 6, is fixed to a cylindrical casing 2. The rotor 5 is then assembled into the cylindrical casing 2 in a freely rotatable manner, as shown in FIGS. 1 and 2.
According to the known method of assembling a cable reel described above, three assembling steps are required:
1) unrolling a flat cable from a coiled reel and temporarily keeping the unrolled flat cable in a looped state; PA1 2) stretching out the spiraled flat cable and joining a connector to each end thereof, and PA1 3) winding the flat cable around the axial direction of a rotor. PA1 a) unrolling the flat cable having a first end portion from a coiled reel; PA1 b) fixing a first connector to the first end portion of the flat cable; PA1 c) preparing the rotor having the barrel portion, and providing the top plate with a fixing notch; PA1 d) fitting the first connector into the fixing notch; PA1 e) winding the flat cable around the barrel portion of the rotor up to a predetermined length as the flat cable is being unrolled from the coiled reel; PA1 f) cutting off the flat cable, so as to form a second end portion; PA1 h) fixing a second connector to the second end portion; and PA1 I) mounting the rotor wound with the flat cable into the cylindrical casing in a freely rotatable manner. PA1 a) unrolling the flat cable having a first end portion from a coiled reel; PA1 b) fixing a first connector to the first end portion of the flat cable; PA1 c) preparing the rotor having the barrel portion, and providing the top plate with a fixing notch; PA1 d) fitting the first connector into the fixing notch; PA1 e) winding the flat cable around the barrel portion of the rotor up to a predetermined length as the flat cable is being unrolled from the coiled reel; PA1 f) cutting off the flat cable, so as to form a second end portion; PA1 g) fixing a second connector to the second end portion; and PA1 h) mounting the rotor wound with the flat cable into the cylindrical casing in a freely rotatable manner, so that the top plate is fitted to the upper-side opening of the cylindrical casing, whereby a cylindrical space is formed between the cylindrical casing and the rotor and the flat cable is contained in the cylindrical space.
This requires the series of steps including temporarily spiraling, straightening, and winding a flat cable. Such a handling process requires considerable labor and costs.
In view of this state of the art, the present invention intends to simplify the above process steps, reduce production costs, and improve productivity.